Appliances that generate heat need a means to regulate internal temperature for adequate overall operation of the appliance. Cavities, passages, or ducts are frequently provided to direct air flow and to cool the appliance. Some appliances have conventionally relied upon natural convection to provide movement of air through ducts to cool the appliance. For example, the higher the expected temperature, the larger the size of the duct and inlet/exhaust ports.
However, the space provided for the ducts usually comes at the expense of space needed for general operation of the appliance. For example, in an oven, the overall size is generally standardized due to cabinet size, etc. By increasing the size of the ducts, the size of the cooking chamber is reduced.
As a result, a fan or blower can be provided to force air through the ducts or ventilation system of the appliance. Incorporating forced air ventilation into the appliance improves the cooling and temperature regulation within the appliance. However, it is important to ensure that the fan or blower is operating properly, that is, producing sufficient airflow, to provide adequate ventilation.
Generally, monitoring the power supplied to the fan is inadequate to determine if proper ventilation of the appliance is taking place. Likewise, using a tachometer system to measure the fan's rotational speed (RPM) can be inadequate to properly determine an actual airflow rate through the appliance. An appliance's controller can determine the amount of current used to run the fan, or measure the speed (RPM) of the motor by a variety of means, but other factors can influence the actual rate of airflow such as clogged or blocked ducts/vents or a stuck rotor shaft/impeller. For example, in the situation of clogged or blocked ducts/vents, the fan will continue to essentially operate normally (the RPM may be slightly higher) and the current detected by the device controller remains relatively unchanged (the current may drop slightly), but because the duct/vent is blocked, there is a reduced airflow provided to the appliance, and portions of the appliance might operate hotter than intended. Without adequate cooling regulation in the appliance, damage may occur to the appliance components, such as control electronics, circuitry, or other components and the life of the affected components may be reduced.
Accordingly, an appliance having a fan that provides for proper and adequate cooling during operation of the device would be useful. Such an appliance that includes an autonomous or separate and independent (aka autonomous) system for determining whether a sufficient flow of air is present would also be beneficial. An appliance capable of taking remedial action in the event the separate system detects that the flow of air is insufficient for properly cooling the device would also be particularly useful.